1. Field of the Invention
The present invention relates to a method for manufacturing an integrated type photovoltaic device.
2. Description of Prior Art
Photovoltaic devices having a plurality of photoelectric conversion elements that are connected in series on a single substrate are well known: as integrated type photovoltaic devices. Currently there are two kinds of the integrated type photovoltaic device in practical use: a first type photovoltaic device and a second type photovoltaic device. The first type photovoltaic device has a multiplicity of photoelectric conversion elements, which are formed by laminating a light-transmitting conductive film, a photoelectric conversion layer comprising thin semiconductor films such as amorphous silicon or microcrystalline silicon to form a p-i-n junction inside, and a rear surface electrode film on an insulating and light-transmitting substrate such as a glass substrate. The light-transmitting conductive film of one photoelectric conversion element is electrically connected with the rear surface electrode film of an adjoining photoelectric conversion element. In this way, the multiplicity of photoelectric conversion elements are serially integrated. When light enters the photoelectric conversion layer through the substrate and light-transmitting conductive film of each photoelectric conversion element, photovoltaic power is generated inside the thin semiconductor films. The photovoltaic power generated in each photoelectric conversion element is added in series through the rear surface electrode film and taken out to an external device.
On the other hand, the second type photovoltaic device has a multiplicity of photoelectric conversion elements, which are formed by laminating a rear surface electrode film, a photoelectric conversion film comprising thin semiconductor films such as amorphous silicon or microcrystalline silicon to form an n-i-p junction, and a light-transmitting conductive film on a substrate having insulative surfaces, for example a metal plate such as a stainless steel plate with an insulating coating, or a plastic plate. The light-transmitting conductive film of one photoelectric conversion element is electrically connected with the rear surface electrode film of an adjoining photoelectric conversion element. In this way, the multiplicity of photoelectric conversion elements are serially integrated. When light enters the photoelectric conversion layer through the light-transmitting conductive film of each photoelectric conversion element, photovoltaic power is generated inside the thin semiconductor films. The photovoltaic power generated in each photoelectric conversion element is added in series through the rear surface electrode film and taken out to an external device.
In a manufacturing process of the integrated type photovoltaic device, techniques of energy irradiation such as laser processing have been typically used. The techniques, however, may cause thermal damages to photoelectric conversion elements. In the case where the energy irradiation is performed from a substrate side instead of the element side to prevent the damages, the substrate must be a transparent insulating substrate such as glass. The quality of the substrate heavily effects on the finished photovoltaic device. On the other hand, when integrating the elements on a metal substrate, electrode layers and a photoelectric conversion layer should be formed separately each time using a metal mask, in order to separate the photoelectric conversion elements and to ensure the electric insulating property between the photoelectric conversion elements and the metal substrate.
Japanese examined patent publication No. 19990/1993 discloses a method of manufacturing a photoelectric conversion device with a non-light-transmitting substrate, wherein a processing for integration is performed mainly from a main surface where a photoelectric conversion layer is formed.
Japanese examined patent publication No. 60273/1993 discloses a processing method of integration using a laser processing in conjunction with an etching technique.
Regarding the method of integration by laser beams disclosed in the application No. 19990/1993, however, there is a concern that some electric currents may leak because the thermal damages provide low resistance regions to the photoelectric conversion layer.
The method using the laser processing and the etching technique requires quite accurate control of laser processing; for example the processing should be stopped halfway through a thin film of 1 μm thick or less. The narrow process window is one of the problems.
The present invention is made to solve the above-described conventional problems and has an object to provide a method of manufacturing an integrated type photovoltaic device in which a rear surface electrode layer, a photoelectric conversion layer and a light-transmitting conductive layer are laminated on a substrate (the second type structure), which can be easily patterned.